Heart patients told \'drugs most effective Doctors have always known that heart attacks are more common in the morning, but have never understood why. Now a team from the Baylor College of Medicine in Houston  found the first molecular proof that the heart has an internal \'biological clock\', which increases the risk of a type of fatal heart attack in the morning.
Ventricular arrhythmia, or abnormal heartbeat, occurs most often after sunrise and causes a high number of deaths.
Our ciracadian rhythm, or \'body clock\' responds to the 24-hour day on Earth and controls things like sleep patterns.
Now scientists, led by Dr Xander Wehrens, have identified a protein called KLF15 that plays an important role in regulating the heart\'s rhythm and also rises and falls in a daily cycle.
The team created mice that had been genetically engineered to either lack Klf15 or make far more of the protein than normal.
All the rodents had a much higher risk of arrythmias compared to their normal counterparts.
\'It is the first example of a molecular mechanism for the circadian change in susceptibility to cardiac arrhythmias,\' Dr Wehrens said.
\'If there was too much Klf15 or none, the mice were at risk for developing the arrhythmia.\'
Scientists said we need stable levels of the protein to keep electrical stability within the heart muscle cells. If the Klf15 levels are not stable this can disrupt the regular beating of the heart, potentially causing arrhythmia.
More than 180,000 people die from heart disease in the UK each year, which is one in three of all deaths.